This invention concerns an apparatus for transilluminating objects as set forth in the preamble of patent claim 1.
An apparatus for recognizing particular explosives or other sought materials in luggage is described in European Patent document EP 0 485 872 A2. In this regard, the luggage is transilluminated from a plurality of directions with two or three X-ray sources in order to create therefrom substantially a three-dimensional density reconstruction of the luggage. The X-ray sources are thereby positionally offset from one another at the two upper corners of a cross-sectionally rectangular transport tunnel, through which luggage pieces are moved. In this regard, two X-ray sources are arranged closely near to and in front of one another. An L-shaped detector line is arranged opposite each of the X-ray sources. Through this apparatus a so-called multi-view is created from three beam directions, with all beam planes extending perpendicular to the transport direction.
International Patent Publication WO 9712229 describes a process and an apparatus for detecting smuggled goods, for example, explosive materials, drugs or money. In this case, a tomograph is used, with whose help a luggage piece indicated to be a smuggled good is viewed from various directions. In one embodiment, an X-ray generator is included in the tomograph. This X-ray generator is thereby attached to a C-arm. A detector device is also mounted on a C-arm, opposite the X-ray generator. The C-arm, and thereby the X-ray generator with the detector device, is moved in continuous planes for taking various pictures. From the determined absorption rate of the items in a luggage piece, an effective atom number Zeff is determined. Simultaneously, the mass and density of the detected item are determined by an algorithm.
An apparatus of the generic type of this invention is described in U.S. Pat. No. 6,088,423 A, which has at least three X-ray sources and three detector apparatus which, with the help of three different ray beam directions, creates a three dimensional image. In this regard, the radiation beam paths lie perpendicular to a transport direction. This uses a large amount of space and means that the apparatus will be large.
German Patent Publication DE198 23 448 A1 describes an apparatus to examine physical items using X-ray radiation in which a mask masks-through an appropriate portion of radiation so that a beam cone is created which is directed toward a linear shaped receiver arranged perpendicular to an object, and which creates time-displaced scan signals from different angular directions.
It is an object of this invention to provide an apparatus of the generic type described above which uses very little space.
This object is achieved by the limitations of patent claim 1.
According to principles of this invention, in order to decrease space requirements, at least two ionized radiation beams from different radiation sources are crossed over with at least one of these radiation beams not perpendicular to a transport direction or the object, and thereby at least two detector apparatus which at least partly cross over one another are directed toward these beams. In this manner, with the help of two beam sources and three detector apparatus, a spatial image of an object being transported can be created by the beams coming from different beam angles toward the object.
Beneficial enhancements are set forth in the dependent claims.
In a preferred variant, with the help of three radiation sources and five detector apparatus, an object to be transilluminated is transilluminated from at least five different directions during its transportation in the apparatus and a quasi 3-D (three dimensional) model of the object is simultaneously created. In this regard, preferably, two of the five detector apparatus are crossed within one another.
It is beneficial in one arrangement to have a front radiation source to the right and a following downstream radiation source to be left and below the transport apparatus. These are offset from one another and mounted along the transport path one behind the other. A third radiation source, contrary to this, is mounted above the transport apparatus. It is also, however, understood that the front radiation source can be arranged above the transport device and the two rear radiation sources can be mounted below the transport device.
Preferably, the detector apparatus are structured as L-shaped detector lines, which are formed of a plurality of detector pairs arranged one behind the other.
Preferably, the apparatus will be used in a multi-view system for automatically determining materials with X-ray beams, whereby, with help of obtain signals, in addition to absorption rate, the thickness or volume (and therefrom the density) of items in a object can be determined. From the absorption rate and the density then the type of material of items in an object which have just been transilluminated can be exactly determined.